A Nobel prize-winning economist has joined shadow chancellor Ed Balls in condemning Mervyn King, the Bank of England governor, for "turning into a cheerleader for the government's policies".

Princeton professor Paul Krugman said King had jeopardised his independence after a series of speeches and interventions in support of the Tory-led coalition's public spending cuts.

Krugman said: "He's wrong on the economics — front-loaded spending cuts are the wrong policy for a still-depressed economy — but that's not the key point; rather, the point is that if you're going to have an independent central bank, the people running that bank have to be careful to stay above the political fray."

David Blanchflower, a former member of the Bank of England's monetary policy committee, said it was noticeable that Ben Bernanke, King's counterpart at the US Federal Reserve, refused to answer questions about government policy.

"It puts the shadow chancellor in a difficult position, because how can he trust the governor to be independent when he wants advice?" he said.

Their criticism followed an attack on the central bank governor by Balls during an interview with the Financial Times. Balls warned King to stay out of the political arena, saying he was putting the Bank's reputation at risk by endorsing the government's "extreme" deficit reduction plans.

Balls, who became shadow chancellor last month after Alan Johnson's resignation, drew comparisons between King's stance and the backing given by the Bank to the Treasury's fiscal hawks during the Great Depression of the 1930s.

"The last thing you ever want is for the Bank of England to be drawn into the political arena," said Balls, who was involved in Labour's move in 1997 to give the Bank independence to set interest rates. "Central bank governors have to be very careful about tying themselves too closely to fiscal strategies, especially when they are extreme and are making their job on monetary policy more complicated."

When presenting the Bank's inflation and growth forecasts on Wednesday, the governor was asked whether he was George Osborne's Plan B, and replied: "There has to be a Plan A. This country needs a fiscal consolidation starting from its largest peacetime deficit ever."

His comments cheered the Treasury, which wants rates maintained at historic lows while it pushes through public-sector spending cuts.

Krugman said: "It brings back memories of Alan Greenspan, who was a stern advocate of fiscal discipline — until a Republican was in the White House, and he suddenly declared that we needed to cut taxes to prevent too rapid a reduction in US debt. It's very sad to see King, who had a good reputation, going down the same path."